[meteorite-list] AD Ungouped irons : NWA 6166 Main Mass and NWA 6167 Last Slice

[Fabien Kuntz]

Hello list, 

these two ungrouped irons have been approved 16 september on the MetSoc Database 
: 


http://tin.er.usgs.gov/meteor/metbull.php?code=51756
http://tin.er.usgs.gov/meteor/metbull.php?code=51757


Both have unusual pattern when etched, both are mineralogicaly interesting : 


NWA 6166 : Iron meteorite, structurally anomalous plessitic octahedrite, 
ungrouped, very low weathering grade.
The matrix surrounding the kamacite  occurs in two different types: some zones 
have a very homogeneous (up to  0.1 mm scale) Ni-rich metal matrix; other zones 
are made of a rather  coarse (10-50 µm) intergrowth of Ni-rich and Ni-poor metal 
arranged into  irregular but continuous ribbons


NWA 6167 : Iron meteorite (silicated), Ni-rich ataxite, ungrouped, very low 
weathering grade
The studied 16.5 cm2 surface contains five rounded silicate inclusion (up to 6.8 
mm in maximum length). They consist of prevailing crystals of olivine 
(Fo79.6±0.6), low-Ca pyroxene (En78-80 Wo2.2-3.1), high-Ca pyroxene (En49-51 
Wo41-42), plagioclase (An78-85), Ca-phosphate and chromite. Close to the 
boundary with the Fe-Ni metal, the silicate crystals are crossed by tiny 
veinlets of very fine-grained Fe-Ni metal+troilite or iron oxyhydroxides.



You can found here the last NWA 6166 I have, the main mass, and the last slice 
of NWA 6167 :

http://wwmeteorites.com/NWA6166-6167.html


The last specimen of NWA 6167, the 95g main mass is available uppon request.


Fabien